The Coin is not respawning after 5 seconds?

I tested this out myself, and it works. Also, I fixed parts in your script

local db = true
script.Parent.Touched:Connect(function(hit)
    if hit.Parent:FindFirstChild("Humanoid") ~= nil then
        if db then
            db = false
            script.Parent.Transparency = 1
            local player = game.Players:GetPlayerFromCharacter(hit.Parent)
            if player then
                player.leaderstats.Coins.Value = player.leaderstats.Coins.Value + 1
                script.Sound:Play()
                script.Parent.Transparency = 1
                wait(5)
                script.Parent.Transparency = 0
                db = true
            end
        end
    end
end)

seemed like the rest of the script was running even though it didn't check to see if it was an actual player, and maybe make this a server script, and check to see if the script isn't disabled